What are the other Names for this Condition? (Also known as/Synonyms)

• Pupils of Different Size
• Unequal Pupil Sizes
• Unequally Sized Pupils

What is Anisocoria? (Definition/Background Information)

• Anisocoria is a relatively common eye condition that is characterized by “Unequal Pupil Sizes”. In other words, the size of the left and right pupils vary in dimension (different sizes)
• Anisocoria may develop from a variety of reasons such as head injury, systemic disorders, medications, and congenital defects. Based on the underlying cause, Anisocoria is classified into several types including:
  • Physiologic Anisocoria: It is the most common type, and it does not usually cause any significant vision impairment
  • Pathologic Anisocoria: It develops from damage to the nerves due to certain congenital/structural defects in the eye
  • Mechanical Anisocoria: The condition develops following an eye injury that damages the iris and other structures
  • Pharmacologic Anisocoria: It is caused by certain medications that may be taken for other health conditions

Who gets Anisocoria? (Age and Sex Distribution)

• Anisocoria is reportedly common among the general population
• Individuals of any age category (both children and adults) may be affected
• Both males and females may be affected
• Worldwide, individuals of all races and ethnicity are prone to Anisocoria and there is no preference observed

What are the Risk Factors for Anisocoria? (Predisposing Factors)

The risk factors for Anisocoria depend on the type of Anisocoria. These may include:

• Physiologic Anisocoria: No clearly established risk factors are identified for this form of Anisocoria
• Pathologic Anisocoria:
  • Aniridia
  • Coloboma
  • Ectopic pupil
• Mechanical Anisocoria:
  • Trauma
  • Inflammatory conditions
  • Tumors
• Pharmacologic Anisocoria:
  • Anticholinergics
  • Sympathomimetics
  • Insecticides

Other causes of Anisocoria include:

• Adie’s tonic pupil
• Autoimmune autonomic ganglionopathy
• Horner’s syndrome
• Oculomotor nerve palsy
• Trigeminal autonomic cephalalgia
• Cluster headache

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Anisocoria? (Etiology)

Anisocoria occurs due to damage or abnormal functioning of the nerves that control the pupil sizes; this results in Unequally Sized Pupils. It may be caused by a variety of reasons.

• Physiologic Anisocoria: The cause is generally unknown
• Pathologic Anisocoria: It develops from damage to the nerves due to certain congenital and/or structural defects in the eye
• Mechanical Anisocoria: The condition develops following an injury that damages the iris and other eye structures
• Pharmacologic Anisocoria: It is caused by certain medications that may be taken for other health conditions

What are the Signs and Symptoms of Anisocoria?

The signs and symptoms of Anisocoria may vary from one individual to another. It depends on several factors, such as the type of Anisocoria, the severity of the condition, and underlying causative factors. However, the characteristic feature of all forms of Anisocoria is the difference in pupil sizes; the difference between the pupils is typically between 0.4 to 0.8 mm, but may even reach 1 mm.

• Isolated Anisocoria is often asymptomatic
• The other signs and symptoms of Anisocoria may broadly include:
  • Light sensitivity and glare from pupil dilation (mydriasis)
  • Impaired accommodation
  • Eye pain
  • Headache
  • Double vision
  • Blurry vision
  • Fatigue
  • Numbness
  • Droopy eyelids
  • Impaired coordination or ataxia
• Associated signs and symptoms of the underlying condition/disorder may also be observed.

How is Anisocoria Diagnosed?

Anisocoria may be diagnosed by the following observations and tests:

• Physical examination and medical history evaluation
• Assessment of signs and symptoms
• General eye exam:
  • Examination of the eye in both dark and lighted environments
  • Using topical eye drops to determine the pupillary size reaction is also helpful in arriving at a possible cause
• Blood and urine tests to diagnose underlying conditions/disorders, as necessary
• Fundoscopic (ophthalmoscopic) examination by an eye specialist, who examines the back part of the eye (or the fundus)
• Visual acuity test using a special and standardized test chart (Snellen chart)
• Slit-lamp examination
• Visual evoked potential (VEP) test
• Fundus fluorescein angiography
• Optical coherence tomography (OCT) of eye
• Imaging studies including CT and MRI scans of the head and neck region

Additional tests and procedures to diagnose the underlying causative condition may be needed.

A differential diagnosis to eliminate other conditions may be considered, before arriving at a definitive diagnosis.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Anisocoria?

The complications of Anisocoria may include:

• Difficulty in performing simple tasks under bright lights
• Vision impairment
• Decreased quality of life
• Treatment related complications

Complications arising from the underlying/associated condition, if any, may be noted.

How is Anisocoria Treated?

The treatment of Anisocoria depends on the type of Anisocoria, its severity, the presenting signs and symptoms, and the underlying causative factor. The treatment measures include treating the symptoms and managing the underlying condition/disorder.

• Physiologic Anisocoria usually does not require any treatment
• Pathologic Anisocoria or Congenital Anisocoria may be treated based on the severity and type of the underlying condition. This may involve the use of eyeglasses, medication, or surgery
• Mechanical Anisocoria due to structural defects may be corrected using surgery. If it is caused by underlying medical conditions, such as glaucoma or uveitis, it can be treated using medications
• Pharmacologic Anisocoria usually gets better on discontinuing the medications/agents that triggered it

Close follow-up and periodic visits to the healthcare provider is important and recommended.

How can Anisocoria be Prevented?

It may be difficult to prevent some cases of Anisocoria. However, the following factors may help reduce one’s risk for developing the same:

• Undertaking early and adequate treatment of any health issues is important
• If there is a family history of a medical condition, then genetic counseling will help assess risks, before planning for a child
• Wear helmets and safety gear while participating in sports or while driving to prevent head/eye injury
• When possible, the offending/causative medications may be discontinued and/or alternative medication prescribed

What is the Prognosis of Anisocoria? (Outcomes/Resolutions)

The overall prognosis of Anisocoria depends on the underlying cause, type, severity of presenting signs and symptoms, age, and the individual’s response to treatment measures.

• Physiologic Anisocoria: The prognosis is generally excellent, since it is a mild condition without any significant signs and symptoms
• Pathologic Anisocoria: The prognosis mainly depends on the underlying causative condition
• Mechanical Anisocoria: The prognosis mainly depends on the underlying causative condition
• Pharmacologic Anisocoria: The prognosis can be improved by removing the offending agent (medication)

Additional and Relevant Useful Information for Anisocoria:

Please visit our Eye & Vision Health Center for more physician-approved health information:

https://www.dovemed.com/health-topics/vision-center/